1. Field of the Invention
The present invention relates to a reagent for sample analysis for analyzing a blood cell in a biological sample, a reagent kit for sample analysis for analyzing thereof, and a method for analyzing thereof.
2. Description of the Related Art
In the field of a clinical test, analysis of a blood cell in a sample is very useful for diagnosing various diseases of a circulatory organ or the like of a subject. Depending on a disease, the number of particular blood cells is increased or decreased, or blood cells which are not usually present appear in peripheral blood in some cases.
In recent years, a variety of automatic blood cell counting devices to which a principle of flow cytometry is applied are commercially available. Using such devices, classification and counting of a blood cell are performed in a general laboratory. When these automatic blood cell counting devices are used, classification and counting of leukocytes in a sample can be automatically performed.
In order to classify and count leukocytes, first, erythrocytes in a blood sample are lysed to prepare a measurement sample. By guiding the prepared measurement sample to a detector and detecting an electric impedance signal, leukocytes can be classified into three kinds. Meanwhile, a leukocyte usually includes the following five kinds; a lymphocyte, a monocyte, a neutrophil, an eosinophile, and a basophil. A leukocyte can be classified into five kinds by further performing fluorescence staining in addition to erythrocyte lysing treatment, irradiating the fluorescently stained blood cell with excitation light, detecting a fluorescent signal and a scattered light signal emitted from the stained blood cell, and analyzing it. Since a basophil is usually small in the number, a leukocyte can be more precisely classified into five kinds by the following method rather than by classification of a leukocyte into five kinds by one time measurement. Based on the property that a basophil is hardly destroyed under an acidic condition as compared with other leukocytes, the number of the basophil is measured by treating a blood sample exclusively for measuring a basophil (see U.S. Pat. No. 5,518,928). Then, by combining the result obtained from measurement of the number of the basophil and the result of leukocyte classification obtained by another method, a leukocyte can be classified into five kinds more precisely.
Here, a problem which frequently arises in leukocyte measurement is appearance of a nucleated red blood cell (NRBC). Since a nucleated red blood cell has a nucleus, a nucleus remains even when a red blood cell is lysing-treated. Thereby, since a nucleated red blood cell has a signal close to that of a lymphocyte in the aforementioned measurement, this gives a plus error at the time of measurement of the leukocyte number. In order to exclude this influence, treatment exclusively for measuring a nucleated red blood cell is performed to measure the nucleated red blood cell number (see U.S. Pat. No. 6,664,110), and the nucleated red blood cell number is subtracted from the leukocyte number obtained by another method, thereby, the precise leukocyte number can be obtained.
However, when a treatment exclusive for a particular blood cell is increased in order to perform precise leukocyte classification, it is laborious and there is a possibility that a device is complicated or is increased in size. In addition, when a plurality of reagents for exclusive use in particular blood cell measurement are used, the cost of a total blood test is increased. From such a viewpoint, it is preferable that a treatment exclusive for a particular blood cell is performed as little as possible.
Meanwhile, a basophil and a nucleated red blood cell can be measured by treating a blood sample under an acidic condition. Therefore, there is a possibility that, when a blood sample is treated under an acidic condition, there is a possibility that both of a basophil and a nucleated red blood cell can be measured by one time measurement. As one of such trials, Japanese Laid-Open Patent Application Publication No. 2002-148261 describes that a basophil and an erythroblast (nucleated red blood cell) can be measured by mixing a sample with an aqueous solution containing a red-blood cell dissolving agent and a surfactant which bring a leukocyte and an abnormal cell into a suitable state for staining, adding a staining solution containing a fluorescent dye to stain it, and measuring a fluorescent intensity and a scattered light intensity with a flow cytometer.
However, in the case of a specimen containing large number of leukocytes, the aforementioned conventional method does not sufficiently separate a basophil and a leukocyte other than a basophil in some cases.